Two kinds of glass beads with mean diameters of 110μm and 210μm were used as sediments in which methane hydrate was formed. Porosities of these glass beads were determined to be 36.3% and 36.8% separately by a volumetric method. Hydrate saturation was estimated and its relative permeability was measured at different stages of methane hydrate formation. Results showed that the formation of methane hydrate in bead packs induces a distinguished decline of permeability. The relationship can be described as an exponential function when the hydrate saturation is under a low value which is not greater than 25%. The parallel capillary model of hydrate occupying the pore center is well fitted with the experimental data. This proved that the methane hydrate was mainly formed in the pores of bead packs but the methane hydrate was not coated on the bead surfaces in experiments.
About 44% of global offshore oil and gas resources are located under the deepwater below 300 meters (Li, 2006). With the rapid increase in the world energy consumption, it becomes an important strategy for many countries to explore and exploit deepwater hydrocarbon resources. Deepwater oil and gas deposits are usually accompanied by natural gas hydrate due to a circumstance with the suitable pressure and temperature. There is strong evidence to show that some submarine slope failures and other geohazards are caused by the gas hydrate dissociation (Nixon, 2007). The effect of gas hydrate dissociation to the deepwater oil and gas exploitation must be taken into account. It is estimated that there may be as much as 1014 to 1016 m3 of natural gas trapped beneath hydrates indicating the hydrate resource to be twice as great as the combined fossil fuel reserve (Sloan, 1998; Makogon, 2007).
